Treat precision as NANOSECONDS for timestamp to be coerced

[Praveen2112]

Description

This will be irrespective of the precision configured or specified as
session property.

Additional context and related issues

Depends on #17900.

Release notes

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# Section
* Treat precision as NANOSECONDS for timestamp to be coerced.

[vlad-lyutenko]

I am a little bit missed, why it's safe to remove it here?
It's because of this change in HivePageSource:

if (fromType instanceof TimestampType timestampType && toType instanceof VarcharType varcharType) {
            // --deleted-- if (timestampType.isShort()) {
            //  --deleted--  return Optional.of(new ShortTimestampToVarcharCoercer(timestampType, varcharType));
            // }
            return Optional.of(new LongTimestampToVarcharCoercer(timestampType, varcharType));
        }

[Praveen2112]

Previously we were respecting the timestamp precision - so we need a coercer which would could have timestamp read as long or it could be as LongTimestamp - but this change would ensure that we would be reading the timestamp column as a NANOSECOND - so we don't need ShortTimestampToVarcharCoercer

[Praveen2112]

@krvikash Thanks for the review. Addressed the comments

[findepi]

squashed to make reviewable

[findepi]

skimmed. looks directionally correct

[huberty89]

Just a question: We are no longer relay on a session?

[Praveen2112]

Previously we rely on the session to determine the timestamp precision so that we could read the timestamp column with that precision and now we would read them as NANOSECOND irrespective of the precision configured.

[krvikash]

LGTM

[Praveen2112]

@krvikash AC